In general terms, the purpose of applying a laser beam to a surface is to modify the surface, its structure and its physical state.
In practice, the mechanism involves a partial fusion of the surface, in the case of the crystallization of amorphous silicon.
The Applicant identified a problem of providing a device and a method for monitoring, in real time, on site, both rapidly and nondestructively, a laser surface treatment in which there are at least two generally similar surface fields to be treated, of given depth, to each of which there is to be applied, on one or more occasions, a laser beam treatment, with characteristics chosen so as to change the physical state of each surface field.
The present invention affords a solution to this problem.